I've been using windows cmd prompt to compile LUFA demo projects for the past few days, but for some reason the make all command won't run anymore and I see the following in cmd prompt:

C:\Users\Cody\Desktop\lufa-LUFA-170418\Demos\Device\ClassDriver\VirtualSerial>make all
/bin/sh: avr-size: command not found
/bin/sh: avr-size: command not found
[INFO] : Begin compilation of project "VirtualSerial"...

make: avr-gcc: Command not found
make: *** [build_begin] Error 127

I have the avr 8 bit toolchain downloaded and added to my PATH as well as the MinGW bin, but regardless; this exact environment was working yesterday so I'm confused why i'm getting Error 127s all of a sudden.

Have you tried the obvious? What if you try to run avr-size (with no parameters) on the command line?

I.e. is it existing and is it in the path?

Then same for "avr-gcc".

A wise man once asked me "so what have you changed since it was working and now?".
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Did you meddle with your PATH, perhaps?

As of January 15, 2018, Site fix-up work has begun! Now do your part and report any bugs or deficiencies here.

No guarantees, but if we don't report problems they won't get much of a chance to be fixed! Details/discussions at link given just above.

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

I didn't meddle with my PATH. The only change I can think of that may have any bearing on this is that I accidentally ran "make clean" and then "make all" in the parent directory of the LUFA demo folder containing the project in question. I re-downloaded the entire LUFA demo directory to verify if this was indeed what was causing the issue but the avr-gcc command still isn't recognized anymore.

I tried running avr-size and avr-gcc with no parameters and got "is not recognized as an internal or external command, operable program or batch file." errors for both :X.

When something behaves differently than yesterday something essential has changed since yesterday. (Computers do not have moods. They are deterministic machines ;-)

If you can't run those commands on a command line but rather get the errors you cite, then those files are not present in a directory pointed to by the PATH variable. Either the PATH variable is not correct, or the files are actually missing.

Double check PATH variable contents, and the actual existence of those executable files.

As of January 15, 2018, Site fix-up work has begun! Now do your part and report any bugs or deficiencies here.

No guarantees, but if we don't report problems they won't get much of a chance to be fixed! Details/discussions at link given just above.

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

JohanEkdahl's suggestion to check that the bin file pointed to the in the PATH actually exists was the winner. My avr8 toolchain folder mysteriously disappeared. After copying it back into the location referenced in my PATH the demos became compilable again. Thanks!

As of January 15, 2018, Site fix-up work has begun! Now do your part and report any bugs or deficiencies here.

No guarantees, but if we don't report problems they won't get much of a chance to be fixed! Details/discussions at link given just above.

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]